As an example of a communication system to which the present invention may be applied, a 3GPP (3rd Generation Partnership Project Long Term Evolution; hereinafter referred to as ‘LTE’), LTE-Advanced (hereinafter referred to as ‘LTE-A’) communication system will now be broadly described.
FIG. 1 illustrates a general view of an E-UMTS network structure as an example of a communication system.
Herein, the E-UMTS (Evolved Universal Mobile Telecommunications System) corresponds to a system evolved from the conventional UMTS (Universal Mobile Telecommunications System). The 3GPP is presently carrying out a basic standardization process for the E-UMTS. Generally, the E-UMTS may also be referred to as an LTE system. For details of the technical specifications of the UMTS and the E-UMTS, reference may be made to Release 8 and Release 9 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network”.
Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), base stations (eNode B; eNB), and an Access Gateway (AG), which is located at an end of a network (E-UTRAN) and connected to an external network. The base stations (BSs) can simultaneously transmit multiple data streams for a broadcast service, a multicast service and/or a unicast service.
One or more cells may exist for one BS. One cell is set to one of bandwidths of 1.25, 2.5, 5, 10, 15, and 20 Mhz to provide a downlink or uplink transport service to several UEs. Different cells may be set to provide different bandwidths. Also, one BS controls data transmission and reception for a plurality of UEs. The BS transmits Downlink (DL) scheduling information of downlink data in the corresponding UE to notify information related to time and frequency domains to which data will be transmitted, encoding, data size, and Hybrid Automatic Repeal and reQuest (HARQ). Also, the BS transmits Uplink (UL) scheduling information of uplink data to the corresponding UE to notify information related in time and frequency domains that can be used by the corresponding UE, encoding, data size, and HARQ. An interface for transmitting user traffic or control traffic can be used between the BSs. A Core Network (CN) may include the AG and a network node or the like for user registration of the UE. The AG manages mobility of a UE on a TA (Tracking Area) unit basis, wherein one TA unit includes a plurality of cells.
The wireless communication technology has been developed up to the LTE based upon Wideband Code division Multiple Access (WCDMA). However, the demands and expectations of the users and the manufacturers and providers are growing continuously. Also, since other wireless access technologies are constantly being developed, the wireless communication technology is required to newly evolve in order to ensure competitiveness in the future. Accordingly, characteristics, such as reduced cost for each bit, extended service availability, usage of a flexible frequency band, simple structure and open interface, and adequate power consumption of the UE are being requested.
Recently, in 3GPP, standardization procedures for a successive technology of LTE have been carried out. In this specification, the successive technology will be referred to as ‘LTE-A’. One of the main differences between an LTE system and an LTE-A system corresponds to a difference in the system bandwidth and the adoption of relay stations.
The LTE-A system is targeted to support a maximum wide band of 100 MHz, and, for this, the LTE-A system is designed to use carrier aggregation or bandwidth aggregation technology that can achieve wide band by using multiple frequency blocks.
In order to use a wider frequency bandwidth, carrier aggregation is designed to use multiple frequency blocks as a single large logical frequency band. The bandwidth of each frequency block may be defined based upon a bandwidth of a system block, which is used in an LTE system. Each frequency block is transmitted by using a component carrier.
Additionally, the reference signal has been newly defined in the LTE-A system. However, detailed research on a method performed by the UE for efficiently and accurately measuring a channel quality state for each network node by using such newly defined reference signal in a wireless communication system including cells configured of multiple nodes has not yet been carried out.